Tinned truffles are either summer or winter truffles (prices vary greatly between the two) that are blanched, and thus canned in their own juices.
They are excellent for vinegarettes, stuffings,and omelets. Some say that the flavor intensifies during the blanching process, the flavor however, does not dissipate and remains the same, or somewhat lighter, but it is definitely there. The most important part of the fresh vs canned is that you are able to actually shave the fresh truffle where as canned truffles should be chopped or sliced. With all fresh black truffles you should put a little heat to them (either in the pan or in the stuffing), the heat helps to bring out the flavor.